Defrost circuit for refrigerator

ABSTRACT

A defrost control for refrigeration apparatus such as a refrigerator-freezer utilizing a single timer motor for cyclically driving an ice maker and effectively continuously timing a series of defrost operations. The timer motor is connected alternatively in parallel with and in series with the compressor motor to provide an improved timing operation.

United States Patent Linstromberg Mar. 14, 1972 [54] DEFROST CIRCUIT FOR Primary Examiner-Meyer Perlin REFRIGERATOR Attorney-James S. Nettleton, Thomas E. Turcotte, Burton H. Baker, Gene A. l-leth, Franklin C. Harter, Anthony Niewyk, Inventor! wllllam Llllstfolllberg, Evansville, Illd- Robert L. Judd and Hofgren, Wegner, Allen, Stellman & Mc- [73] Assignee: Whirlpool Corporation Cord [22] Filed: June 17, 1970 211 App]. No.: 46,922 [571 ABSTRACT 52 us. Cl ..62/157, 62/233, 62/276 A defrost control for refrigeration apparatus such as a s 1] Int. Cl ..F25d 21/06 refrigerator-freezer utilizing a single timer motor for cyclically [58] Field of Search ..62/l35, 137, 138, 157, 188, riving an i e m ker nd effectively continuously timing a se- 62/233, 234, 276 ries of defrost operations. The timer motor is connected alternatively in parallel with and in series with the compressor [56] References Cited motor to provide an improved timing operation.

FOREIGN PATENTS OR APPLICATIONS 9 Claims, 3 Drawing Figures Canada 62/234 DEFROST CIRCUIT FORREFRIGERATOR BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to refrigeration apparatus and in particular to control means for use in refrigeration apparatus.

2. Description of the Prior Art In one form of refrigeration apparatus a timer motor is provided for cyclically driving an automatic ice maker, a second timer motor is provided for timing a cyclical operation of a defrost heater so as to permit operation of the defrost heater on a time cycle independently of the cycle of operation of the ice maker. It has been proposed to utilize a single timer motor to provide both operations, such as by permitting the ice maker timer motor to run continuously but periodically disconnecting the drive therefrom to the ice maker.

SUMMARY OF THE INVENTION The present invention comprehends an improved control utilizing such a single timer motor and circuit means for connecting a timer motor selectively in parallel with and in series with the compressor motor of the refrigeration apparatus. The timer motor is arranged in the circuit in one form of the invention so as to operate in parallel with the compressor motor during the normal operation of the refrigeration apparatus. However, upon the commencement of a defrost operation, the timer motor is connected in electrical series with the compressor motor. In another form of the invention the timer motor is connected for operation concurrently with the compressor under the control of the cabinet thermostat during the normal operation of the apparatus. In this circuit the timer motor is also connected in electrical series with the compressor during the defrost operation.

The circuit includes a single switch for connecting the ice maker timer motor for such alternate operation. The switch causes the timer motor to be selectively connected in series with the defrost heater or with the compressor to provide the desired alternative operations.

BRIEF DESCRIPTION OF THE DRAWING Other features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawing wherein:

FIG. 1 is a fragmentary perspective view of a refrigeration apparatus embodying the invention;

FIG. 2 is a schematic wiring diagram of an electric control circuit embodying the invention; and

FIG. 3 is a schematic wiring diagram of a modified control circuit embodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the exemplary embodiment of the invention as shown in FIGS. 1 and 2 of the drawing, a refrigeration apparatus generally designated includes a cabinet 11 defining a freezer compartment 12 and an above freezing refrigerator compartment 13. An automatic ice maker 14 is mounted in the freezer compartment for automatically forming ice bodies. A cabinet thermostat 15 may be provided within one of the chambers of cabinet 11 for controlling the operation of the refrigeration apparatus. The refrigeration apparatus illustratively may comprise a compressor 16, a condenser 17, a capillary l8 and an evaporator 19 within the walls of the cabinet 11. Such refrigeration apparatus is well known in the art and requires no further description here.

Operation of the ice maker 14 is conventionally controlled by a timer motor 20 as shown in FIG. 2. The present invention comprehends an improved circuit generally designated 21 for controlling timer motor 20 to permit the use thereof both for driving the automatic ice maker 14 and controlling an evaporator defrost operation by means of a defrost heater 22. The control is effected in circuit 21 by means of a single defrost switch generally designated 23 which, as shown in FIG.

2, may comprise a single pole double throw switch having fixed contacts 23a and 23b and moving contact 23c.

As shown in FIG. 2, moving contact 23c of switch 23 is connected to one power supply lead L'l. Defrost heater 22 is con nected through a defrost bimetal switch 24 to switch contact 23b. The other side of heater 22 is connected to the other power supply lead L2. Timer motor 20 is connected between switch contacts 23a and 23b. A water valve solenoid 25 for controlling delivery of water to the ice maker mold is connected in series with a water valve switch 26. The series connection of solenoid 25 and switch 26 is connected in parallel with timer motor 20.

Compressor motor 27 is connected through a cabinet thermostat switch 28 to fixed contact 23a. The'other side of the compressor motor is connected to power supply L2. A condenser fan motor 29 and an evaporator fan motor 30 are connected'in'parallel'with compressor motor 27.

In operation, control circuit 21 in its normal refrigeration arrangement, is arranged with switch contact 230 engaging contact 23a. Thus, timer motor 20 is connected from power supply lead Ll through switch 23, defrost bimetal 24 and defrost heater 22 to power supply lead L2 whereby the timer motor may operate to time the freezing of a batch of ice and drive the ice maker '14 through its cyclical ice making operations. The timer motor is also connected to effectively continuously operate to serve as a clock for the timing of the evaporator defrost cycle. At this time the compressor motor is controlled by the cabinet thermostat switch 28 so as topermit normal cyclical operation of the compressor as well as the condenser fan and evaporator fan. As shown, the timer motor further controls water valve switch 26 for use in the cyclical making of ice bodies in ice maker 14.

When the timer motor times out the refrigeration period to initiate a defrost operation, the timer motor causes moving switch contact 230 to be thrown from fixedcontact 23a to fixed contact 23b. This places heater 22 directly across the power supply thereby effecting a defrost heating operation. The heating operation continues until defrost bimetal switch 24 opens or the defrost operation period is timed out by motor 20 to restore moving switch contact 230 to the position shown in FIG. 2 in engagement with fixed contact 23a. During the defrost operation timer motor 20 is effectively connected in series with compressor motor 27 through cabinet thermostat switch 28 and remains energized. The impedance of the compressor motor windings is very small compared to the impedance of the timer motor windings and therefor most of the line voltage is dropped across the timer which precludes operation of compressor motor 27.

Thus, the single selector switch 23 alternately connects the timer motor for operation through the compressor motor windings during a defrost operation and for independent continuous operation duringthe normal refrigeration operation of the apparatus.

Turning now to the embodiment of FIG. 3, a modified control circuit 121 is shown to comprise a control circuit generally similar to control circuit 21 but having a modified arrangement of the cabinet thermostat switch 28. Thus, as shown in FIG. 3, cabinet thermostat 28 is connected to defrost switch fixed contact 230 and through a common connection 131 to compressor motor 27 and timer motor 20. Each of the other elements of circuit 121 is similar to corresponding elements of circuit 21 and is numbered herein similarly.

The operation of control circuit 121 differs from that of control circuit 21 in that the timer motor 20 in control circuit 121 operates only when the compressor motor 27 is operated in the normal refrigeration cycle. When the defrost switch 23 is thrown to engage moving contact 23c with fixed contact 23b, heater 22 is energized directly across the power supply through switch 24, and timer motor 20 and compressor motor 27 are connected in series between the power supply leads. Thus, the timer motor runs continuously during the defrost operation.

Upon the timer motor returning switch contact 230 to the refrigeration position engaging fixed contact 23a, the circuit is reestablished to discontinue the defrost operation and again permit cycled control of the compressor motor 27 and timer motor 20 by the cabinet thermostat switch 28. Since the time required to freeze water in an ice maker is proportional to the amount of time the compressor operates, the circuit of FIG. 3 is preferable where maximum ice making capability for a time cycle ice maker is desired. This concept is shown in my US. Pat. No. 3,040,542, entitled Product Level Control for Ice Maker."

Normally the defrost switch 24 opens prior to the end of the timed period of the defrost cycle controlled by timer motor 20. Defrost bimetal switch 24 is made to be responsive to a temperature condition, such as adjacent evaporator 19, to provide an effectively positive indication of the completion of the defrost operation. Thus, momentarily upon return of the switch 23 to the normal refrigeration position shown in full lines in FIGS. 2 and 3, the timer motor ordinarily will not be energized. However, as soon as the refrigeration condition in the evaporator lowers the temperature below the reset temperature of the defrost bimetal switch, the circuit is once again established from the timer motor to power supply lead L2 through heater 22 to commence the continuous operation of the timer motor foreffecting the timing of the defrost cycle periods.

The foregoing disclosure of specific embodiments is illustrative of the broad inventive concepts comprehended by the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a refrigeration apparatus having a compressor motor for effecting a refrigerating cycle operation of the apparatus, a defrosting means for effecting a defrosting operation, and means for forming ice bodies including a water delivery valve and a solenoid for operating said valve, control circuit means including: a timer having an electric motor for controlling operation of saiddefrosting means and driving said means for fonning ice bodies; first switch means controlled by said timer for (a) connecting the timer motor in series with said compressor during a defrosting operation and (b) connecting the timer motor in parallel with the compressor motor during a refrigeration cycle; and a second switch means controlled by said timer for energizing the water delivery valve solenoid concurrently with said timer motor.

2. The refrigeration apparatus of claim 1 wherein said first switch means comprises a single pole double throw switch.

3. The refrigeration apparatus of claim 1 wherein said first switch means is controlled by said timer motor.

4. The refrigeration apparatus of claim 1 further including a thermostat switch for controlling energization and deenergization of said compressor motor and timer motor concurrently during a refrigeration cycle.

5. The refrigeration apparatus of claim I further including a thermostat switch for controlling energization of said compressor motor independently of said timer motor during a refrigeration cycle.

6. The refrigeration apparatus of claim I further including a thermostat switch for controlling energization of said timer motor through the compressor motor windings during a defrosting operation.

7. The refrigeration apparatus of claim 1 further including means for discontinuing operation of the timer motor during a refrigeration cycle as an incident of a high temperature condition.

8. In a refrigeration apparatus control for controlling operation of a compressor motor and a defrost heater, circuit means comprising: switch means for connecting one side of an electrical power supply alternatively to one side of said compres sor motor and said defrost heater; means for electrically connecting the other side of said compressor motor and said defrost heater to the other side of the electrical power supply;

a timer motor electrically connected across said switch means to be connected in series with said defrost heater to said one side of the power supply in parallel with said compresor motorwhen the switch means is disposed to connect said compressor motor to said one side of the power supply and to be connected in series with said compressor motor to said one side of said power supply in parallel with said defrost heater when the switch means is disposed to connect said defrost heater to said one side of the power supply; and a thermostat switch connected in series with the compressor motor between the compressor motor and the connection of the timer motor to the switch means for cycling the compressor motor as a function of a sensed temperature condition whereby said timer motor is controlled by said thermostat switch when the switch means is disposed to connect said defrost heater to said one side of the power supply and operates independent of said thermostat switch when said switch means is disposed to connect said compressor motor to said one side of the power supply.

9. The refrigeration apparatus of claim 8 further including a temperature responsive switch in series with said defrost heater for preventing operation of the defrost heater as a 

1. In a refrigeration apparatus having a compressor motor for effecting a refrigerating cycle operation of the apparatus, a defrosting means for effecting a defrosting operation, and means for forming ice bodies including a water delivery valve and a solenoid for operating said valve, control circuit means including: a timer having an electric motor for controlling operation of said defrosting means and driving said means for forming ice bodies; first switch means controlled by said timer for (a) connecting the timer motor in series with said compressor during a defrosting operation and (b) connecting the timer motor in parallel with the compressor motor during a refrigeration cycle; and a second switch means controlled by said timer for energizing the water delivery valve solenoid concurrently with said timer motor.
 2. The refrigeration apparatus of claim 1 wherein said first switch means comprises a single pole double throw switch.
 3. The refrigeration apparatus of claim 1 wherein said first switch means is controlled by said timer motor.
 4. The refrigeration apparatus of claim 1 further including a thermostat switch for controlling energization and deenergization of said compressor motor and timer motor concurrently during a refrigeration cycle.
 5. The refrigeration apparatus of claim 1 further including a thermostat switch for controlling energization of said compressor motor independently of said timer motor during a refrigeration cycle.
 6. The refrigeration apparatus of claim 1 further including a thermostat switch for controlling energization of said timer motor through the compressor motor windings during a defrosting operation.
 7. The refrigeration apparatus of claim 1 further including means for discontinuing operation of the timer motor during a refrigeration cycle as an incident of a high temperature condition.
 8. In a refrigeration apparatus control for controlling operation of a compressor motor and a defrost heater, circuit means comprising: switch means for connecting one side of an electrical power supply alternatively to one side of said compressor motor and said defrost heater; means for electrically connecting the other side of said compressor motor and said defrost heater to the other side of the electrical power supply; a timer motor electrically connected across said switch means to be connected in series with said defrost heater to said one side of the power supply in parallel with said compressor motor when the switch means is disposed to connect said compressor motor to said one side of the power supply and to be connected in series with said compressor motor to said one side of said power supply in parallel with said defrost heater when the switch means is disposed to connect said defrost heater to said one side of the power supply; and a thermostat switch connected in series with the compressor motor between the compressor motor and the connection of the timer motor to the switch means for cycling the compressor motor as a function of a sensed temperature condition whereby said timer motor is controlled by said thermostat switch when the switch means is disposed to connect said defrost heater to said one side of the power supply and operates independent of said thermostat switch when said switch means is disposed to connect said compressor motor to said one side of the power supply.
 9. The refrigeration apparatus of claim 8 further including a temperature responsive switch in series with said defrost heater for preventing operation of the defrost heater as a result of a high temperature condition whereby said timer motor is permitted to operate only when said temperature responsive switch is closed and when said switch means is disposed to connect said compressor motor to said one side of the power supply. 